Currently, in the conventional fabricating process of the low temperature polysilicon thin film transistor (LTPS TFT), when the low temperature polysilicon layer is defined with source and drain contact areas, it is required to use a mask for defining the areas for ions implant, and then an ion implantation equipment is applied to implant a certain amount of phosphorus ions for forming the source and drain contact areas. However, the cost of the ion implantation equipment is very high, and the ion implant process is very complicated.